You can etch flexible circuit boards using a 3d printer. They can be made of very thin copper clad board material or even conductive fabric.

Standard copper clad circuit board material (FR4) of any thickness, can also be etched using this method.

Step 1: How It Works

PLA, Nylon, ABS and most common filaments used for 3d printing do not stick to copper well enough to lay down a pattern that can be etched to create a circuit board. A fairly new elastomeric rubber filament is now available that sticks quite well to copper. It is called Ninjaflex. In fact, it sticks quite well to almost anything including acrylic, blue painters tape, and glass.

A circuit board pattern can be drawn in a free program like 123D Design and then extruded to a thin thickness and saved as an STL file. It can then be printed on top of a thin copper clad board or plated conductive fabric: step 1 pic. It can then be etched in the standard way with a Ferric Chloride solution.

The circuit board shown was printed at standard breadboard and perfboard spacing of traces at .1" centers. This fits standard through hole components and some surface mount ones. Pic 2 shows the finished circuit, a Picaxe microcontroller.

If you want a thin and light circuit, this layout works well. To get more flex, the components would have to be spaced further apart.

Step 2: Supplies

Access to a 3d filament printer. I used a Makerbot Replicator 2 but other printers with the right extruder should work.

White Ninjaflex filament. I also tried black and water clear Ninjaflex filament but they did not stick near as well as the white. Other colors might work.Available from Adafruit: http://www.adafruit.com/products/Or:http://www.3dsupplyworld.com/flexible/

123D Design or other 3d program that can create and manipulate STL files.

Ferric Chloride available from: http://www.mpja.comOther etchants may work, but I have not tried them.

Fine steel wool.

Acetone- available from WalMart

Duct tape

Step 3: Draw The Circuit Pattern

Draw ItI used 123d design Beta to make the circuit board pattern. It was drawn and then extruded to .011" thick.

I designed it to make the traces on .1" centers. They are .06" wide with a .04" gap between them. This is standard breadboard spacing which fits through hole components and some surface mount components.

Spacer BarA spacer bar is then added on the side of the pattern which the 3d printer extruder will reach first. The idea is for the bottom of the spacer bar to sit on the base and the top of the spacer bar to be at the height of the bottom of the circuit board pattern.

When it is printed it prints the spacer bar first on the base and then jumps to the circuit board material and starts printing at the right height to accommodate the thickness of the circuit board material. This works well for the 3 thin circuit board materials mentioned in Supplies. They all have a thickness of about .07" and a spacer of .004" worked well.

If you are using a thicker circuit board material you will have to extrude the bottom of the spacer bar to allow for the extra thickness.

circuitpat.stl

circuitpat.stl107 KB

Step 4: Fine Tune Your 3D printer

To print using ninjaflex, you will need to fine tune your 3d printer. This will take some fiddling around.A heated bed is not required.

Check Your ExtruderNinjaflex is a bit tricky to print out and will only work on printers that have the right drive block for the extruder. For an older Replicator 2 you must install Makerbots upgrade kit which includes a spring and a roller bearing. You must also download from Thingiverse the new drive block for the kit and print it out.

If you have a different 3d printer, you should check out Thingiverse for drive blocks that use a spring and roller bearing that will fit your printer. There should be a very small gap (orange arrow) below the bearing and drive gear and the hole where it goes into the hot end of the extruder. Ninjaflex is like a wet noodle and an excessive gap here will allow it to flex and jam.

Level The BedThere is a very small margin of error for printing a thin coating on copper. To close and the extruder will clog, too far, and it will not stick well enough to etch.

Your bed has to be very flat and very, very level. Nothing else will do.

Use calibration.stl to fine tune the leveling of the bed. Print it onto the middle of the bed in PLA. Measure all the ends and make sure they are within .002" of each other in thickness. Do Not skip this step.

Make A Trial PrintUsing circuitpat.stl, print the circuit board pattern in Ninjaflex directly on the printer bed. Mark the edges of the pattern on the bed and then peel off the pattern. Use it to cut flexible circuit board material larger than the pattern.

Replicator 2 SettingsThese settings work well for a Replicator 2. If you use a different printer, you may have to play with the settings.

Step 5: Fasten The Circuit Board Material

The thin flexible board material (scissor cut) has to be dead flat on the print bed with no bumps or curls. I tried taping it down and got bad results. The only thing that has worked so far is to use spray-on adhesive on the bottom of the board.

First rub the top of the circuit board with fine steel wool to remove any oxidation. Then take it outside and spray it on the bottom side with the spray adhesive. Then bring it inside and stick it on the printer base while it is still fairly wet. Use a piece of rounded flat plastic to burnish it down, working from the center out.

Step 6: Print the Circuit Pattern

Print the circuit pattern and then check to see how well it sticks to the copper circuit board. If it smears around, it is too close and you will have to adjust the STL file in 123D Design and thicken the spacer bar. If it does not adhere well you may have to make the spacer bar thinner.

Step 7: Etch The Circuit

Carefully peal off the Ninjaflex printed board from the printer base. Be careful not to put any pressure on the printed Ninjaflex. Now is a good time to remove any adhesive residue from the bed. Use duct tape and burnish it down and then peal it off. Repeat until bed is clean.

Use Acetone to remove any adhesive residue sticking to the bottom of the board. This will allow the bottom copper cladding to be etched off. Then place the board into standard Ferric Chloride etching solution. My scissor cut boards took about 40 minutes at room temperature. Remove and clean well with water.

Step 8: Etching Conductive Fabric

If you want even more flexible circuits, you can etch conductive fabric. This is particularly useful if you want to make a circuit that will be continuously flexed such as a ribbon cable or led strip lights.

You can etch conductive fabric in the same manner as described in the previous steps. The only addition you must make is to attach some of the self sticking shelving material to the bottom of the circuit board. Measure it. If the shelving material and fabric is thicker than about .007" you may have to adjust the spacer bar in the Stl file. Spray adhesive on the attached shelving material and burnish the fabric down on the printer base.

Conductive fabric etches very fast. The one in the picture took about five minutes.

Pic 3 shows the Adafruit Pyralux board that was etched the same way. The board material is very thin, less than .001"

You can use this conductive paint (CuPro-Cote PAINT) to glue on components:

http://lessemf.com/paint.html

Keep in mind that glued components are not nearly as sturdy as soldered components.

Or you can make your own conductive glue: http://www.instructables.com/id/Make-Conductive-G...

Step 9: Other Possibilities

Surface Mount Circuit BoardsThe sample circuit board has the traces set at .1" centers. The thinnest traces I have etched so far are about .03" wide on .05" centers. This spacing will fit a SOIC sized surface mount IC just fine.

Here is a way I like to mount SOIC sized components on etched breadboards: http://www.instructables.com/id/Picaxe-Projects-1...

Using NinjaflexNinjaflex is a very interesting material that can be used to print all kinds of other things besides circuit boards. It is quite tough and cut resistant, yet it is quite flexible. It can be used to print wallets, hinges, tubes, lanterns, flashlights, and other sturdy things.

Flexible Circuit Boards Without A 3D PrinterYou can hand cut the shelf liner material into circuit patterns and etch boards that way. You will, of course, be limited by your ability to cut precisely.

Details can be found here: http://www.instructables.com/id/Curved-Circuit-Ar...And here:http://www.instructables.com/id/Curved-Circuit-Boa...

If you leave a fair amount of copper on the boards you can make permanently curved boards (step 9 pic).